In fusing two vertebral bodies or setting a bone fracture, it is common practice to use a securing mechanism to hold the bone or vertebral bodies in place while the bone tissue fuses or heals. A commonly used securing mechanism is referred to as a bone plate. A bone plate aids the healing process by maintaining the fractured bone or vertebral bodies in a stable position. Once positioned, it is also desirable for the bone plate to remain securely fastened in place.
A bone plate is typically held in place by surgical screws or other appropriate devices inserted through openings in the bone plate. Because bone fractures and vertebrae structure vary from person-to-person and from bone-to-bone, a bone plate designed to allow variable placement of the surgical screws through the plate is desirable.
Prior adjustable bone plates have incorporated a two rack styled apparatus to allow for adjustable alignment of the plate and variable placement of screws in the bone tissue. A typical prior device comprises a lower plate having a toothed rack and an upper plate having an opposing toothed rack. The upper and lower plates may be placed together in various positions allowing variable placement of screws along the longitudinal axis of the bone plate. The rack on the upper plate is placed on the rack of the lower plate at the desired location and the appropriate screws are inserted through the plates and into the bone. Positive engagement between the opposing racks on the upper and lower plates provide some stability in the longitudinal direction of the bone plate. A major drawback to this type of system is that it provides, generally only stability and variable screw location in a longitudinal direction. Unfortunately, these prior art devices do not provide adequate stability or variability in screw placement in longitudinal, lateral or diagonal directions.